In accordance with a preferred embodiment of the present invention, there is provided a unique internal core profile for a nozzle airfoil of a gas turbine, preferably the first stage nozzle, which enhances the performance of the gas turbine. It will be appreciated that the external shape of the nozzle airfoil improves its interaction with the buckets forming the stages of the turbine. Concomitantly the internal core profile shape of the nozzle airfoil is also significant for structural reasons as well as to optimize internal cooling with appropriate wall thickness. The nozzle airfoil internal core profile is defined by a unique loci of points which achieve the necessary structural and cooling requirements whereby improved turbine performance is obtained. This unique loci of points define the internal nominal core profile and are identified by the X, Y and Z Cartesian coordinates of Table I which follows. The 1,200 points for the coordinate values shown in Table I are for a cold, i.e., room temperature nozzle airfoil at various cross-sections of the nozzle airfoil along its length. The positive X, Y and Z directions are axial toward the exhaust end of the turbine, tangential in the direction of engine rotation looking aft and radially outwardly toward the outer platform, respectively. The X and Y coordinates are given in distance dimensions, e.g., units of inches, and are joined smoothly at each Z location to form a smooth continuous internal core profile cross-section. The Z coordinates are given in inches in distances along radii from the turbine axis. Each internal core profile section in the X, Y plane is joined smoothly with the adjacent profile sections in the Z direction to form, using the Table I coordinate values, the complete internal nozzle airfoil core profile.
Table I provides coordinate values for the complete internal core airfoil shape passing through the inner and outer platforms and the airfoil therebetween. The physical shape of the internal core profile between the inner and outer platforms is given in Table I by the airfoil sections defined between Z value limits of 22.200 and 25.050.
It will be appreciated that as each nozzle airfoil heats up in use, the internal core profile will change. Thus, the cold or room temperature profile is given by the X, Y and Z coordinates for manufacturing purposes. Because a manufactured internal nozzle airfoil core profile may be different from the nominal profile given by the following table, a distance of ±0.030 inches from the nominal profile in a direction normal to any surface location along the nominal profile defines a profile envelope for this internal nozzle airfoil core profile. The profile is robust to this variation without impairment of the mechanical cooling and aerodynamic functions of the airfoil.
In accordance with a preferred embodiment of the present invention, there is provided a turbine nozzle segment including inner and outer platforms and an airfoil extending between the platforms, the airfoil having an internal nominal core profile at least a portion of which is substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I between Z value limits of 22.200 and 25.050, wherein the Z values between the limits are radial distances from a turbine axis to planes extending normal to the radii and wherein the X and Y values are distances in inches which, when connected by smooth continuing arcs, define internal core profile sections at each distance Z along the airfoil between said Z value limits, the profile sections at the Z distances between the limits being joined smoothly with one another to form the airfoil internal core profile.
In accordance with a further embodiment of the present invention, there is provided a turbine comprising a plurality of nozzle segments arranged in a circumferential array about an axis of the turbine, each nozzle segment including inner and outer platforms and at least one airfoil extending between the platforms, each airfoil having an internal nominal core profile at least a portion of which is substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I between Z value limits of 22.200 and 25.050, wherein said Z values between the limits are radial distances from a turbine axis to planes extending normal to the radii and wherein the X and Y values are distances in inches which, when connected by smooth continuing arcs, define internal core profile sections at each distance Z along the airfoil between the Z value limits, the profile sections at the Z distances between the limits being joined smoothly with one another to form the airfoil internal core profile.
In accordance with a further embodiment of the present invention, there is provided a turbine nozzle segment including inner and outer platforms and an airfoil extending between the platforms, the airfoil having an internal nominal core profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I wherein the Z values are radial distances from a turbine axis to planes extending normal to the radii and wherein the X and Y values are distances in inches which, when connected by smooth continuing arcs, define internal core profile sections at each distance Z along the airfoil, the profile sections at the Z distances being joined smoothly with one another to form the airfoil internal core profile.
In accordance with another embodiment of the present invention, there is provided a turbine comprising a plurality of nozzle segments in a circumferential array about an axis of the turbine, each segment having inner and outer platforms and at least one airfoil extending between the platforms, each airfoil having an internal nominal core profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I wherein the Z values are radial distances from the turbine axis to planes extending normal to the radii, and wherein the X and Y values are distances in inches which, when connected by smooth continuing arcs, define internal core profile sections at each distance Z along the airfoil, the profile sections at the Z distances being joined smoothly with one another to form the airfoil internal core profile.